fix(tasks): a create that names a status is stamped like an update to it (#3683)

build_note (create_note and create_records) set the status and nothing it
implies, so create_task(status="in_progress") wrote a started task with no
started_at, and done/cancelled had no completed_at or next recurrence.
The transition is now one function, apply_status_transition, called by
both paths; tests pin the invariant for every status.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_services_notes.py

@@ -8,6 +8,8 @@ MCP, recurrence, snippets — gets it by construction rather than by remembering
 These test the helper directly. The point of the change is that there is now ONE
 place to test.
 """
+import pytest
+
 from scribe.services import notes as notes_svc
 
 # --- inline embedding (#2056) -----------------------------------------------
@@ -69,3 +71,36 @@ def test_embed_note_swallows_an_indexing_failure():
     note = MagicMock(id=5, user_id=42, title="T", body="B")
     with patch("asyncio.create_task", side_effect=ValueError("model gone")):
         notes_svc.embed_note(note)          # must not raise
+
+
+# --- #3683: a create that names a status is the transition an update is ------
+
+_LIFECYCLE = ("started_at", "completed_at", "recurrence_next_spawn_at")
+
+
+@pytest.mark.parametrize("status", ["todo", "in_progress", "done", "cancelled"])
+def test_a_task_created_at_a_status_matches_one_updated_to_it(status):
+    """The invariant, not the instance that surfaced it: which lifecycle
+    stamps a row carries must not depend on whether it was created at a status
+    or reached it by update. Recurrence is included because done/cancelled
+    schedule the next spawn."""
+    rule = {"type": "interval", "unit": "week", "every": 1}
+    created = notes_svc.build_note(1, title="t", status=status, recurrence_rule=rule)
+
+    updated = notes_svc.build_note(1, title="t", recurrence_rule=rule)
+    updated.status = status
+    notes_svc.apply_status_transition(updated)
+
+    for field in _LIFECYCLE:
+        assert (getattr(created, field) is None) == (getattr(updated, field) is None), (status, field)
+
+
+def test_a_task_created_in_progress_knows_when_it_started():
+    note = notes_svc.build_note(1, title="t", status="in_progress")
+    assert note.started_at is not None
+    assert note.completed_at is None
+
+
+def test_a_note_with_no_status_gets_no_lifecycle_stamps():
+    note = notes_svc.build_note(1, title="t")
+    assert all(getattr(note, f) is None for f in _LIFECYCLE)